Scraper assembly for waste treatment tanks

ABSTRACT

In waste treatment tanks having overflow weirs on the sides thereof, a scraper assembly in which scraper blades are each pivoted to a lowered position on the tank floor with the blade ends extending beneath the weirs, and a raised position in which the blades are positioned above the weirs, without additional movement of the scraper blades along the pivot axes. The pivot axes are angled rearwardly and/or downwardly from the tank edge to achieve this operation.

United States Patent 1191 Fechter [54] SCRAPER ASSEMBLY FOR WASTE TREATMENT TANKS [75] Inventor: Leonhard Fechter, Michelbach,

1 Germany [57] ABSTRACT Assigneel Savant-wakes Michelbacher In waste treatment tanks having overflow weirs on the I-Iutte,Germany sides thereof, a scraper assembly in which scraper blades are each ivoted to a lowered osition on the F p p [22] Aug 1971 tank floor with the blade ends extending beneath the [21] Appl. No.: 173,467 weirs, and a raised position in which the blades are positioned above the weirs, without additional movement of the scraper blades along the pivot axes. The Y [52] US. Cl ..2l0/527 pivot axas are angled rearwardly and/or d dl [51] Cl. ..Bold from the tank edge to a hieve operation [58] Field of Search ..2l0/523-53l, 298 1 [56] 10 Claims, 2 Drawing Figures 1 UNITED STATES PATENTS 2,670,080 2/1954 Scott ..2l0/527 2,779,471 1/1957 Knapp ..210/527 x I I I p111 3,709,370 [4 1 Jan. 9, 1973 Primary Examiner-Samih N. Zaharna Assistant Examiner-T. A. Granger Attorney-Larson, Taylor and Hinds PAIENTEDJAN 9191s 3.709.370

F/G. Z LEONHARD -T ATTORNEYS SCRAPER ASSEMBLY FOR WASTE TREATMENT TANKS BACKGROUND OF THE INVENTION as sedimentation tanks normally include a travelling bridge with scraper blade assemblies mounted thereon for movement along the tank. Usually these assemblies are divided transversely into two equal sections. Such tanks, in particular rectangular or secondary tanks, are provided with overflow weirs extending longitudinally along the parallel long sides of the tank with their thicknesses projecting into the clear section of the tank above the floor thereof. These overflow weirs therefore present an impediment to simple operation of the conventional longitudinally movable scraper assemblies. The scraper bladescannot be hoisted completely out of the water because their outer edges are interferred with by the bottoms of the overflow weirs. If the scraper blades remain submerged, however, the task of return ing or moving these scraper blades to another position to start a new active run thereof is hampered. If the travelling speed of the scraper blades is increased while the scraper blades are still submerged, this will cause a strong turbulence in the water which will hinder the sedimentation of the sewerage sludge or stir up sludge already settled. On the other hand, if the inactive or idle run of the blade is too slow, the overall efficiency of the scraping operation is diminished.

Hence, there exists a need for an improved arrangement for moving scraper blade assemblies during inactive or idle runs.

SUMMARY OF THE INVENTION Thus, it is a purpose of the present invention to provide in combination with a waste treatment tank having overflow weirs a new and improved arrangement for returning scraper blade assemblies during idle runs thereof including an arrangement for raising the scraper blades above the surface of the water in a simplified manner without interference from the overflow weirs.

This purpose of the present invention is achieved by providing an arrangement in which each scraper blade assembly is mounted for pivoting movement between its raised and lowered position about an axis which extends at an angle with respect to a reference line which is horizontal and perpendicular to the side wall adjacent the scraper blade assembly. This axis may extend in a horizontal plane but forwardly or rearwardly of the said reference line (preferably rearwardly) or it may lie in the same vertical plane as the reference line but inclined downwardly from the side of the tank. Alternatively, the pivoting axis may extend downwardly and to one side or the other of a vertical plane passing through the reference line.

With any of the above arrangements, when the scraper blade is moved from its lower position to its upper position, it describes an arcuate path wherein the edge of the scraper blade which was initially beneath the weir moves inwardly, by-passing the weir as it moves above the same.

In the usual arrangement, the tank will include a pair of scraping blades arranged side by side and extending, in toto, across substantially the entire width of the tank. Since overflow weirs -will normally be provided along both longitudinal sides of the tank, both of the scraper blade assemblies will be constructed in accordance with the present invention such that the outer ends of their respective scraper blades lie beneath their respective weirs in the lowered position and move clear of the weirs as they are raised above the height of the weirs. When using this arrangement including a pair of scraper assemblies, both constructed in accordance with the present invention, the ends of the scraper assemblies adjacent each other start to overlap while the two scraper assemblies are being lifted. To facilitate overlapping, in a preferred embodiment of the invention, the scraper assemblies are staggered relative to the direction of travel. It is quite sufficient to stagger them just a few centimeters.

With the present invention, the improvement is provided whereby the scraper blades of the sludge collecting tankcan be lifted even though the tank is equipped with overflow weirs which extend out into the tank and even though the scraper blades, in their lowered posi tion, extend outwardly to a point near the side wall of the tank, but in any event beneath the weirs. Theadvantages of an elongated tank such as a rectangular tank can therefore be fully realized. Though the two assemblies are moving in slightly opposed directions, they can be lifted simultaneously by a single lifting hoist. Further, the present invention can be applied to existing waste treatment tanks of the mentioned type without requiring any major alterations thereof. It is therefore possible to avoid expensive constructions wherein the scraperblades would have to be shifted horizontally along their pivoting axes before being lifted. I

It is of particular advantage if the pivoting axes of the adjacent scraper assemblies are arranged to form a V viewed from above with the point of the V rearwardmost. With this arrangement the scraping blades form a V collecting the sludge from both sides of the tank and moving it into acentrally arranged sludge channel from which the sludge can be conveniently withdrawn.

When the scraper blade assemblies are hoisted at the end of an active run, their outer edges gradually moving inwardly and above the overflow weirs, the scraper blades emerge from the water. The scraper blades can then be returned or moved into position for a further run with the scraper blades out of the water.

Thus, it is an object of the present invention to provide in an elongated waste treatment tank having at least one longitudinally extending overflow weir, a means for conveniently moving a scraper blade out of the water to facilitate movement of the same during the idle run thereof.

It is another object of this invention to provide, in an elongated waste treatment tank of the type having overflow weirs along the long sides thereof and a pair of scraper blade assemblies movable along the tank, a means for facilitating movement of the blade assemblies out of the water'to simplify return movement of the scraper blades.

It is another object of this invention to provide, in an elongated waste treatment tank having overflow weirs,

a means for mounting scraper blade assemblies for simplified movement between a lowered position in which the scraper blades extend to points near the side walls of the tank under the overflow weirs to a raised position above the overflow weirs wherein the scraper blade assemblies completely by-pass the overflow weirs as they are raised.

Other objects and the advantages of the present invention will be apparent from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

Like numerals represent like elements throughout the several views.

In FIG. 1, the numeral 1 represents a cross-section through an elongated waste treatment tank such as a sedimentation tank. The tank may be either annular or rectangular. To facilitate discussing the invention, it will be assumed that the tank of FIG. 1 is in fact an elongated rectangular tank, the figure being taken in a transverse plane. A pair of overflow weirs 2 extend along the upper part of the two long sides of the tank, and the water level is of course up to the inner edge of these weirs.

A bridge 3 is mounted on the tank 1 to ride along the two long sides by means of rollers 15. Extending downwardly from the bridge 3 are pairs of bearings 7 which support scraper assemblies permitting the same to pivot about axes 6 while preventing movement of the scraping assemblies along their respective axes 6. Each scraper assembly includes a scraper blade 4 mounted to move along the bottom of the tank and vertical rods 5 connecting the scraper blade 4 to the upper part of the scraper blade assembly which is mounted in the bearings 7. In the embodiment of FIG. 1, the two axes 6 are inclined downwardly towards the center of the tank as shown in the figure and these axes lie in the plane of the paper, that is in a vertical plane which is perpendicular to the sides of the tank 1.

In operation, when it is desired to lift the scraper blades 4 above the level of the water, they are turned about the axes 6, the scraper blades 4 following arcuate paths represented symbolically by arrows 8 and 9 in FIG. I. As is evident, as the scraper blades 4 follow this path, they move upwardly and inwardly. The position of the scraper blades are shown in dotted lines as they pass by the weirs 2. After this they continue upwardly above the level of the liquid at which position they are ready for movement during an inactive or idle run of the scraper assemblies. As is also evident from FIG. 1,

as the scraper blades 4 are raised concurrently, their inner adjacent edges overlap transversely. To assure that this overlap occurs with one of the two scraper blades above the other, and without these two inner ends interferring with each other, the scraper blades are staggered at least a few centimeters in the direction of travel.

FIG. 2 shows another embodiment of the invention. FIG. 2 shows a rectangular tank although the features of this embodiment are also applicable to an annular tank. This embodiment differs from FIG. 1 in the arrangement of the axes 6. In this case, the axes are horizontal but angled rearwardly from the outside of the tank inwardly to the center thereof whereby the two axes 6 form a V which is open in the direction of travel which is indicated by the arrow 10.

As with the embodiment of FIG. 1, in the lowered position the scraper blades 4 extend across the bottom of the tank to a point close to the side walls thereof beneath the overflow weirs 2; and upon being lifted, the

scraper assemblies move inwardly clearing the overflow weirs 2 as shown in FIG. 2 in dotted lines after which the scraper blades 4 are raised above the level of the water for movement through an idle or inactive run. The V arrangement of the scraper blades, when viewed from above, is particularly suitable when conveying sludge into a centrally arranged channel 1 1.

In accordance with another embodiment of the invention, the axes 6 'may be inclined both downwardly and rearwardly. This embodiment would be precisely illustrated in the existing figures, considering FIG. 2 as a plan view of FIG. 1. In this case, as with the embodiment of FIGS. 1 and 2 as previously described, the scraper blades 4 would in the lower position extend beneath the overflow weirs 2 and in the raised position move inside of the overflow weirs 2, overlapping and being movable above the level of the water.

Although the invention has been described in considerable detail with respect to a preferred embodiment thereof, it will be apparent that the invention is capable of numerous modifications and variations apparent to those skilled in the art without departing from the spirit and scope of the invention.

Iclaim:

1. In combination, an elongated waste treatment tank having an overflow weir extending longitudinally along an upper portion of a side wall of the tank with its thickness projecting out into the tank above the floor thereof, a bridge including a scraper assembly mounted thereon for movement along the tank, said assembly including a scraper blade, means for mounting said scraper blade on the bridge for pivoting movement about an axis between a lowered position in which the scraper blade is on the floor of the tank and a raised position in which the scraper blade is above the height of the weir, the end of said scraper blade extending to a point near a wall of the tank beneath the weir when the scraper assembly is in the lowered position, said pivoting axis being at an angle to a reference line which is horizontal and perpendicular to the side wall of the tank such that when the scraper assembly is turned about its said axis, the scraper blade rises to a height above that of the weir withoutlateral movement of the scraper assembly along its pivoting axis, and by passing the weir.

2. The invention of claim 1, said a horizontal plane.

3. The invention of claim 1, said pivoting axis lying in the same vertical plane as the reference line' and inclined downwardly from the side wall of the tank.

4. The invention of claim 1, said pivoting axis inclined downwardly from the side of the tank and forming an acute angle with a vertical plane passing through the said reference line.

5. In combination, an elongated waste treatment tank having a pair of parallel overflow weirs extending longitudinally along the upper portions of parallel side walls of the tank, the thickness of each weir projecting out into the tank above the floor thereof, a bridge including a pair of scraper assemblies mounted side by side thereon for movement along the tank, each pivoting axis lying in scraper assembly including a scraper blade, means for mounting each scraper assembly on the bridge for pivoting movement about an axis between a lowered position in which the scraper blade is on the floor of the tank and a raised position in which the scraper blade is above the height of the weir, the end of each scraper blade extending to a point near its respective wall of the tank beneath its respective weir when that scraper blade is in the lowered position, each said pivoting axis being at an angle to a reference line which is horizontal and perpendicular to the side wall of the tank such that when each scraper assembly is turned about its said axis, the scraper blade rises to a height above that of its respective weir without lateral movement of the scraper assembly along its pivot axis, and by passing the weir.

6. The invention of claim 5, wherein the tank is rectangular, and the weirs extend along the longitudinal parallel sides thereof.

7. The invention of claim 5, each said pivoting axis lying in a horizontal plane such that the two pivot axes form a V with the inner adjacent ends of the two scraper assemblies rearmost relative to the direction of travel.

8, The invention of claim 5, wherein each said pivoting axis lies in the same vertical plane as the said reference line and is inclined downwardly from its respective side of the tank.

9. The invention of claim 5, wherein the two said pivoting axes are inclined downwardly from their respective sides of the tank and form an acute angle with a vertical plane passing through the said reference line such that the two pivoting axes form a V when viewed from above with the inner adjacent ends of the scraper assemblies rearwardmost.

10. The invention of claim 5, wherein the inner adjacent ends of the two scraper blades are staggered in the direction of travel. 

1. In combination, an elongated waste treatment tank having an overflow weir extending longitudinally along an upper portion of a side wall of the tank with its thickness projecting out into the tank above the floor thereof, a bridge including a scraper assembly mounted thereon for movement along the tank, said assembly including a scraper blade, means for mounting said scraper blade on the bridge for pivoting movement about an axis between a lowered position in which the scraper blade is on the floor of the tank and a raised position in which the scraper blade is above the height of the weir, the end of said scraper blade extending to a point near a wall of the tank beneath the weir when the scraper assembly is in the lowered position, said pivoting axis being at an angle to a reference line which is horizontal and perpendicular to the side wall of the tank such that when the scraper assembly is turned about its said axis, the scraper blade rises to a height above that of the weir without lateral movement of the scraper assembly along its pivoting axis, and by passing the weir.
 2. The invention of claim 1, said pivoting axis lying in a horizontal plane.
 3. The invention of claim 1, said pivoting axis lying in the same vertical plane as the reference line and inclined downwardly from the side wall of the tank.
 4. The invention of claim 1, said pivoting axis inclined downwardly from the side of the tank and forming an acute angle with a vertical plane passing through the said reference line.
 5. In combination, an elongated waste treatment tank having a pair of parallel overflow weirs extending longitudinally along the upper portions of parallel side walls of the tank, the thickness of each weir projecting out into the tank above the floor thereof, a bridge including a pair of scraper assemblies mounted side by side thereon for movement along the tank, each scraper assembly including a scraper blade, means for mounting each scraper assembly on the bridge for pivoting movement about an axis between a lowered position in which the scraper blade is on the floor of the tank and a raised position in which the scraper blade is above the height of the weir, the end of each scraper blade extending to a point near its respective wall of the tank beneath its respective weir when that scraper blade is in the lowered position, each said pivoting axis being at an angle to a reference line which is horizontal and perpendicular to the side wall of the tank such that when each scraper assembly is turned about its said axis, the scraper blade rises to a height above that of its respective weir without lateral movement of the scraper assembly along its pivot axis, and by passing the weir.
 6. The invention of claim 5, wherein the tank is rectangular, and the weirs extend along the longitudinal parallel sides thereof.
 7. The invention of claim 5, each said pivoting axis lying in a horizontal plane such that the two pivot axes form a V with the inner adjacent ends of the two scraper assemblies rearmost relative to the direction of travel.
 8. The invention of claim 5, wherein each said pivoting axis lies in the same vertical plane as the said reference line and is inclined downwardly from its respective side of the tank.
 9. The invention of claim 5, wherein The two said pivoting axes are inclined downwardly from their respective sides of the tank and form an acute angle with a vertical plane passing through the said reference line such that the two pivoting axes form a V when viewed from above with the inner adjacent ends of the scraper assemblies rearwardmost.
 10. The invention of claim 5, wherein the inner adjacent ends of the two scraper blades are staggered in the direction of travel. 